JP3452271B2 - Telecommunications network - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a telecommunications network consisting of terrestrial equipment such as terrestrial switching centers and satellites for transmitting certain types of communications.

[0002]

BACKGROUND OF THE INVENTION Telephone systems have made great strides in the last quarter century. Today, telephone systems use geostationary satellites that fly 36,000 km above the transmission point, and these satellites are exactly the telephone center of space. However, progress is not limited to this point. The new plan, which is about to take place, will allow every individual, anywhere, to communicate with any point on Earth using a small set of portable transceivers. In fact, telecommunications systems using moving spatial constellations of orbiting satellites are being seriously considered for telephone and communication systems.

Such telecommunications systems are basically carried out using small satellites installed in low orbits. Spatial arrangements to build telecommunications networks for exchanging information between fixed or mobile users (ships, aircraft and vehicles) distributed in limited service areas (eg United States or Europe) or globally. All satellites in the constellation can be used. These types of communication systems make it possible to meet the growing needs for new services such as links between portable terminals, mobile telephones and services related to communication systems.

[0004] In order to carry out and spread such a service, two main approaches are currently under consideration. • Regional communications limited to one country or a few countries (USA, Europe, etc.). -Worldwide communication, where the system covers all points on the earth. In the following explanation, when we say "link between satellites",
Means a link constructed through a ground station,
When referring to “inter-satellite reciprocal link”, it should be understood to mean a direct link between satellites.

FIG. 1 shows the spatial arrangement of a telephone network, whether it is portable or not.
The call originated from the telecommunications terminal 3 is locally transmitted. The structure currently used to provide regional telephone services is based on the spatial arrangement of satellites 4 ensuring visibility or field of view of the service area 1 in which the network of ground stations 2 is formed. The ground station 2 manages or controls communications, manages or controls the relay (handover) process (i.e. link continuity), and enables interconnection with existing terrestrial telecommunications networks. However, the size of such networks depends on the arrangement of the networks of ground stations. Services relate to the placement of stations on the ground, which makes the network regional.

FIG. 2 shows the structure of the spatial arrangement of the telephone network that enables worldwide communication. In such networks, intersatellite links are realized,
It is designed to transmit communications over the space network and limit the network of ground stations. If it becomes possible to transmit communications over the space network, the coverage area of the telephone communication system will no longer be related to the location of the terrestrial network and will be determined solely by the visibility characteristics of the spatial location.

The following publications describe what is currently known on this subject. [BES 78] Day. C. DC BESTE “Design of Satellite Constellations for Optimal to maximize continuous coverage
Continuous Coverage) ”, IEEE Trans. On Aerospace a
nd Electronic Systems, Vol. AES-14, No.3, pp. 466-4
73, May 1978. [BAL 78] A. H. AH BALLARD “Rosette Constellations o
f Earch Satellites) ”, IEEE Transactionson Aerosp
ace and Electronic Systems, Vol. AES-16, No.5, Sep
t. 1980. [BIN 87] are. Binder, S. Day. Hoffman, Ai. Grants, pee. A. Bena (R.BINDER, S.
D.HUFFMANN, I.GURANTZ, PA VENA) “Crosslink Architectures for a multi-satellite system
Multiple Satellite System) ”, Proceedings of the IE
EE, Vol.75, No.1 pp.74-82, Jan. 87. [IRI 90] Federal Communic
Motorola Satellite Commu
Application by nications, Inc. “IRIDIUM, A Low Earch Orbit Mobile Satellite Sys
tem) ”Washington DC, Dec. 90).

[KAT 92] J. Kanyle, J. Takei, S. Shimamoto, Wai. Onozato, tea. Usu, eye. Oka, tea. Kawabata (J.KANIYIL, J.TAK
EI, S.SHIMAMOTO, Y.ONOZATO, T.UTSUI, I.OKA, T.KAWAB
ATA) “A Global Message Network Employing Low EarchOr
biting Satellites) ”, IEEE Selected Areas in Comm
unications, Vol.10, No.2, pp.418-427, Feb. 92. [MAR 91] Gee. Mailell and J. J. Derider (G.MARAL and JJDERIDDER) “Basic Concepts of Low Ea for Communication
rch Orbit Satellite System for Communications) ”T
elecom Paris-ENST, 1991. [RID 86] El. L. RIDER “Analytic Design of Satellite Constella using tilted circular orbit
tions for Zonal Earth Coverage Using Inclined Circ
ular Orbits) ”, The Journal of Astronomical Scienc
es, Vol.34, No.1, January-March 1986, pp. 31-64. [RID 87] El. Rider and W. S. Adams (L.RIDER and WSADAMS) “A circular polar space arrangement (Cir that provides single or multiple coverage over a particular latitude.
cular Polar Constellations Providing Single or Mul
tiple CoverageAbove A Specific Latitude) ”The Jou
rnal of Astronomical Sciences, Vol.35, No.2, April
-June 1987, pp.155-192. [WAL 77] J. Gee. Walker (JG WALKER) “Continuous Whole-Earth Coverage by Circul
ar-Orbit Pattern) ”Technical Report 77044, Royal A
ircraft Establishment, March 24, 1977.

Of all the systems described in the above publications,
Reference is made to the “IRIDIUM” ® program. The plan is designed for global transmission, with the recent trend being to use 66 small satellites in low orbit linked to terrestrial switching centers located around the world. Is configured. According to this plan, a satellite receives a call originating from a portable terminal device and transmits it to another satellite via an inter-satellite link or a local call to a ground station visible from this satellite. To do.

[0010]

To this end, each satellite is equipped with a device capable of establishing a large number (four or more) of intersatellite links. This device is 4-6
It is heavy and complicated because it is equipped with individual antennas and a mechanism for controlling their directions. Given that 90% of the traffic is regional, in order to achieve 10% of the international traffic, the complexity involved in building intersatellite links according to this method should be avoided. I think that the. The present invention is intended to overcome these drawbacks.

[0011]

That is, the present invention is as follows.
It connects two concepts. -Enables transmission of all traffic. • Minimize the extra complexity associated with global transmission compared to local transmission systems. The geographical structure of the network proposed in the present invention further simplifies the management and control of telecommunications, and significantly reduces the path selection problem caused by the spatial arrangement with multiple intersatellite links. .

More specifically, according to the present invention,
In a telecommunications network consisting of multiple switching centers on the ground and spatial arrangements of satellites in low earth orbits, the spatial arrangement is mainly composed of several sets of satellites, which are either polar or It has an orbit in a plane that includes an axis slightly tilted with respect to the polar axis, and the set is designed so that it can communicate in groups of two satellites that are placed in the same orbit, and within the service area. At any point on the ground (whether it be a sending point or a destination point) is visible to at least one satellite of the satellite set, and at least one exchange center is installed at a high latitude, At least one satellite of each satellite set is always visible to the switching center, and the switching center forms a link between satellites that are not in the same orbit. Telecommunications network, such as is provided.

According to the invention, each satellite has equipment for establishing two intersatellite links, one intersatellite link for communicating with satellites located upstream in orbit, The other intersatellite link is adapted to communicate with satellites located downstream in orbit. According to the present invention, for example, eight satellites make up one set, and the space arrangement is made up of five sets. The same set of satellites orbits in the same orbit and is in the sky above the visibility range of the exchange center installed at a high latitude. Five orbits intersect. Other features and advantages of the invention are described below with reference to the figures. The following description does not limit the invention. 1 and 2
And 3 have already been described in the description of the prior art.

[0014]

FIG. 4 is a schematic diagram of a telecommunications network of the present invention. This figure shows the spatial arrangement of satellites in orbit at an angle to the polar axis. According to the invention, this spatial arrangement consists of several sets of satellites distributed over orbits 20 in a plane containing the polar axis P or an axis slightly tilted with respect to the polar axis P. And the so-formed orbital plane intersects on two areas on the ground located at very high latitudes. In accordance with the present invention, in one (or both) of these areas located at very high latitudes, the network has a terrestrial switching center 10 which calls from satellites passing through its field of view. It is designed to exchange calls. This exchange center eliminates inter-satellite links between satellites in different orbits. That is, the switching center interconnects satellites in different orbits.

According to the invention, the number of inter-satellite links is limited to two for each satellite. Each satellite in the same orbit is equipped with a device capable of forming an inter-satellite reciprocal link as described above only with the satellites before and after it in orbit. In other words, the inter-satellite mutual link forming device is limited to two antennas, one for the satellite located behind in orbit,
And the other is aimed at the satellite in front of it in orbit. The network further includes terrestrial communication stations 11 distributed on each continent and adapted for regional communication. In other words, in the case of regional communication, for example, a call sent from a mobile terminal device is received by a satellite that is within the field of view (visibility) of the area in which the call is sent to the recipient of the communication. To the regional communication station that functions as a repeater.

In the case of international communication, the call sent from the mobile terminal device is sent through the orbital surface to the visibility area of the exchange center located at a very high latitude. The call is forwarded to the switching center, which in turn forwards it to a satellite in an orbit plane that can be transmitted to the recipient.

FIG. 5 shows the interconnection of the orbital planes by a high latitude exchange center. In this figure, an exchange center 10 located at or near the North Pole is shown. Of course, instead of or in addition to the exchange center located at the North Pole, another exchange center may be provided at or near the South Pole.

FIG. 6 shows a specific example of the spatial arrangement according to the present invention. In this example, satellites are installed in orbits at an altitude of 1500 km, and 40 satellites are arranged in 5 orbital planes in one orbit. 8 pieces are arranged in each, and the visibility is designed to cover the whole world. In FIG. 6, the numbers P1 to P5 are sung on the five orbital planes. FIG. 6 illustrates the limit condition of the visibility L of the two satellites 4 arranged in the orbital plane P1 with respect to the exchange center installed at a very high latitude as shown in the figure. The location of this exchange center is chosen to interconnect all track surfaces. FIG. 6 shows exactly the geographical requirements for the latitude of the exchange center, which are required for all orbital planes to be interconnected through the exchange center. According to this example, a very high latitude exchange center can be constructed, for example in Iceland.

[Brief description of drawings]

FIG. 1 shows a spatial arrangement structure of a prior art telephone network that enables regional transmission.

FIG. 2 shows a spatial layout structure of a prior art telephone network that enables worldwide transmission.

FIG. 3 shows a prior art spatial arrangement with four or six inter-satellite inter-satellite links per satellite.

FIG. 4 is a schematic diagram of a telecommunications network according to the present invention.

[Fig. 5] Through an exchange center installed at high latitude,
The schematic diagram showing mutual communication of the orbital planes.

FIG. 6 is a schematic diagram showing geographical conditions for visibility of stations.

[Explanation of symbols]

1 ... Service area 2 ... Ground station 3 ... Telecommunication terminal 4 ... satellite 10 Ground exchange center 11 ... Ground communication station 20 ... orbit P ... Polar axis P1, P2, P3, P4, P5 ... Raceway L ... visibility

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Gerard Malal France 31120 Goylan Balandra 18 (56) Reference JP-A-2-179035 (JP, A) US Patent 3497807 (US, A) (58) Field (Int.Cl. ⁷ , DB name) H04B 7/195

Claims (2)

(57) [Claims] 1. A terrestrial exchange center and a spatial arrangement of satellites in low earth orbits, the spatial arrangement consisting of several sets of satellites, the satellites of these satellite sets being polar axes or relative thereto. The satellites, which have an orbit that is a plane including a slightly tilted axis and are placed in the same orbit, can communicate with each other in a group of two satellites. , Regardless of whether it is a sending point or a destination point
Visible to at least one satellite of the satellite set, at least one switching center being installed at high latitude such that at least one satellite of each satellite set is always visible from the switching center. A telecommunications network characterized by the fact that this switching center forms links between satellites that are not in the same orbit. 2. Each satellite has a device for establishing two inter-satellite interlinks, one intersatellite interlink communicating with a satellite located upstream in orbit and the other intersatellite interlink. The telecommunications network according to claim 1, wherein the telecommunications system communicates with a satellite located downstream in orbit.